Paper making wire



Oct. 12, 1965 J. E. WATSON PAPER MAKING WIRE 2 Sheets-Sheet 1 Filed Nov.25, 1960 INVENTOR. James .5. W: 7:50

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ArraeA/e'yj United States Patent 3,211,606 PAPER MAKING WIRE James E.Watson, Appleton, Wis., assignor to Wisconsin Wire Works, Appleton,Wis., a corporation of Wisconsin Filed Nov. 25, 1960, Ser. No. 71,663 4Claims. (Cl. 162-348) This invention relates to a method of making paperand full twill weave wire used therein.

The definition of twill as commonly used in describing a Fourdrinierwire is a weave in which the warp strands cross over one and under twowhile the shute strands cross under one and over two. The term fulltwill as used herein refers to a weave in which both warp and shutestrands cross over two and under two. Such a weave may be produced byusing four heddle frames operating in sequence as follows:

1and4up 4and3up 3and2up 2and1up the sequence thereupon being repeated. Adiagonal pattern is ordinarily a pronounced feature of full twill and isemphasized in the weaving of wire by the fact that the knuckles of fulltwill weave have heretofore been asymmetrical. Full twill weave inmeshes exceeding 100 mesh is commonly used in filters but filter mesh offull twill weave would not be appropriate for the wire of a paper makingmachine both because it would not give adequate drainage and because theasymmetrical knuckles would pattern the paper.

A full twill weave paper making Wire for use in connection with thepresent invention differs from previously known paper making wire notonly in being full twill weave but in being substantially symmetrical inits knuckle structure. For print paper manufacture the wire desirablyhas its relatively broad warp and shute knuckles in common planes on itspaper making face to provide greatly increased an improved pulp supportsurface. Due to the breadth and the symmetry, a relatively large portionof each knuckle contributes to the support of the pulp. The resultingpaper has little or no Wire mark and therefore provides a far superiorsurface for printing.

Despite the increased support area and increased hearing area of fulltwill weave wire made as herein disclosed, there is not only noreduction in drainage but in many cases, an increase in the facilitywith which the liquid drains from the pulp. There is very definitelyimproved fiber orientation and retention to produce paper more rapidlyand to produce paper of better quality than heretofore. In consequenceit is possible to use about three different meshes to cover the entirerange of paper making requirements in lieu of six or seven meshes whichis the minimum heretofore required.

Moreover, a full twill weave wire wears longer than the conventionalwire, does not curl, produces the desired retention and orientationwithout being subjected to oscillation and has less tendency to crackalong the edges than standard wires as heretofore known.

It will of course be understood that both the warp and shute diametersmay be varied to achieve certain results. However, the preferredpractice of the present invention deviates from standard practice in theuse of shute wire which is smaller in gauge than the warp. For example,with 70 mesh warp of .00775 wire, the present invention contemplates theuse of 60 mesh shute, of .00725". In normal practice the shute would be.008" or larger.

The improved fiber orientataion is attributable to the lack of anylongitudinal or diagonal pattern. Reference has already been made to thefact that print paper made 3,211,606 Patented Oct. 12, 1965 as hereindisclosed has little or no wire mark. The full twill weave withsymmetrical knuckles providing greatly increased support surface notonly eliminates wire mark but eliminates the diagonal pattern of valleysor grooves which is characteristic of a twill weave which does not havesymmetrical knuckles. If the wire has a weave such that there arewell-defined grooves or valleys having any component of directionlongitudinally of the wire, there will be a tendency for the fiber to beoriented parallel to this pattern by lodging in such grooves.

The present invention contemplates the use of a wire which either has asubstantially planiform support surface or, for tissue manufacture, awire having slight ribs at right angles to the path of wire movementwhereby further to interfere with the natural tendency of the fibers toalign themselves in the direction of such an advance.

In the making of tissues, there is additional deviation fromconventional practice in that the shute knuckles, rather than the warpknuckles, are raised. In all paper manufacture, despite all efforts toadjust the stock speed to that of the wire, there is an inevitabletendency to align the fiber longitudinally of the wire. This isparticularly noteworthy when tissue is being made. Also the short fibersand filler tend to be lost through the mesh while the longer fibersremain with longitudinal orientation. Conventionally this results intissue paper which tears much more easily longitudinally of the web thantransversely thereof, the ratio of tensile strength usually ranging from3 to 1 to 7 to 1. If the wire is full twill and the shute knuckles areraised slightly above the warp knuckles as herein disclosed, therelative tensile strength in a direction transversely of the web is verygreatly increased by the random orientation of the fiber. Also there ismuch greater retention of the short length fiber which would normallyescape during initial deposit of the pulp. The ratio is reduced below 2to 1 on the average. The transverse tensile strength is three times asgreat as heretofore.

In summary, there is better formation resulting from random fiberdistribution; there is freer drainage; there is better stock retentionwhich not only reduces loss of short fiber but results in better use ofexpensive fillers; better printing surfaces are provided, the two facesof the paper being substantially alike; the belt has longer life,requires less power to drive it, guides more easily on the papermachine, and occasions less wear on suction boxes, requires nooscillation, has less tendency to crack on the edges.

In the drawings:

FIG. 1 is a fragmentary diagrammatic view of the portion of a papermaking machine which includes the stock box and the wire.

FIG. 2 is avery much enlarged fragmentary detail view in plan of a fulltwill wire made in accordance with the invention.

FIG. 3 is a fragmentary detail view taken in cross section on the line33 of FIG. 2.

FIG. 4 is a fragmentary detail view in cross section taken on the line44 of FIG. 2.

FIG. 5 is a view similar to FIG. 3 showing a modified embodiment.

FIG. 6 is a view similar to FIG. 4 showing the embodiment of FIG. 5.

The diagrammatic showing in FIG. 1 exemplifies the invention by showingone type of paper making machine. Except for the wire 10 which has thespecial mesh hereafter described, FIG. 1 is intended to represent onetype of generally conventional apparatus in which a head box 11discharges the stock or furnish 12 over a lip 13 onto the paper makingface A of the wire 10, the support face B of which is mounted on a drumor drums 14, one of which constituted means for driving the wire. In thetype of machine selected to exemplify the invention, an adjustable sliceor gate 15 regulates the flow of the stock from the stock box onto themoving wire. The stock or furnish conventionally comprises pulp in anaqueous vehicle but reference thereto is by way of example and not byway of limitation. The paper making wire is an endless screen, the endsof its warp strands being in butt connection between shute strands atnormal spacing.

The wire 10 differs from conventional practice in many respects, some ofwhich have been enumerated above. In the first place, contrary toconventional practice, the paper making area of the wire is a full twillin which each of the warp strands 20 and the shute strands 25 crossesover two and under the next two, the points of crossing being offset inboth directions so that the knuckles present diagonal patterns as shownby the shading in FIG. 2 and hereinafter described.

While the use of shute strands of smaller gauge than the warp strands isnot an essential feature of the invention it is a preferred feature. Inthis respect the practice of the present invention differs sharply fromconventional practice wherein the shute is ordinarily as large or largerthan the warp. In one particular wire, I use 70 warp strands to theinch, each strand being .00775 in diameter. The shute strands in thiswire are 60 to the inch and .00725 in diameter. In wire of thischaracter the shute would normally be .00825 or larger in diameter and58 shute strands would be used to the inch. Whereas conventional twillhas openings ranging from square to rectangular in a longitudinaldirection, the full twill of the present invention has openings whichordinarily vary from square to rectangular in a transverse di- Irection.

FIGS. 3 to 6 are reproductions of actual photomicrographs enlarged 125times. (The drawings, however, are slightly reduced in scale.) FIG. 3shows a shute strand 25in profile and warp strands 20 in section. Onenoteworthy feature of the wire herein disclosed consists in the factthat all of the warp strands 20 are spaced substantially uniformlytransversely of the wire as clearly appears in FIG. 3.

Moreover, the structure is substantially symmetrical in all respects,the knuckles 21 of the warp strands 20 being offset upwardly forsubstantially the identical distance that the knuckles 22 are offsetdownwardly. Moreover, the upwardly offset knuckles 26 of the shutestrand 25 are substantially at the level of the knuckles 21 of the warpstrands 20 while the downwardly formed knuckles 27 of shute strand 25are substantially at the identical level of the knuckles 22 of the warpstrands 20.

Not only are the several strands uniformly spaced but it will beobserved that each knuckle is substantially symmetrical on a relativelylong radius of curvature as it passes over or under the strands which itcrosses. This shape can be altered by warp tension and by the physicalspecifications of the warp and by control of the position of the shed attime of beat up. Thus the knuckle 26 which is at the top center asviewed in FIG. 3 is approximately midway between the knuckles 22 overwhich it crosses and it is also approximately centered beneath theknuckles 21. The slope of the curve of the knuckle to the left isapproximately identical with its slope to the ri ht.

FIG. 4 shows the warp strand profile of the same wire, the warp beingshown at 20 with upward knuckles at 21 and a downward knuckle at 22. Theshute strands 25 shown in section have upward knuckles 26 and downwardknuckles 27. As in the shute strand profile of FIG. 3 symmetry isevident, the shute strands being substantially uniformly spaced and theknuckles of the warp strand 20 being symmetrically curved.

As will be noted, there is some deformation of the shute strand ratherthan the warp strand wherever the wires cross. Thus, in FIG. 3, theshute strand 25 has been somewhat grooved transversely at 28 during beatup i by the pressure engagement of the warp strand 20.

In each instance the groove 28 is also apparent in FIG. 4 in a certainamount of flattening of the shute strands 25. This is partlyattributable to the use of a smaller gauge shute strand than isconventional in semi-twill for a given mesh; and partly due to thephysical specifications of the warp and shute as to yield point, tensilestrength and elongation; and partly due to the form of the shed used inthe loom; and partly due to the relative tension imposed on the strandsand on the heddles which control them; and partly due to control of therapidity and impact of beat up. These various factors are impossible ofdefintion mathematically but their control is within the skill of theart once it is pointed out what result is to be accomplished. Actually,lighter impact is used to beat up the full twill as disclosed than isused in making the semi-twill as heretofore used. The deformation of thestrands results in pressure interlock of the strands at points ofcrossing to stabilize the resulting wire against diagonal distortionwhen used in a paper machine.

The wire shown in FIGS. 5 and 6 is likewise full twill and isspecifically designed for production of light tissues under ten pounds.One difference lies in the fact that at least on the paper-making facethe knuckles 260 of the shute strands 250 rise materially above thelevel of the knuckles 210 of the warp strands 200. Each depressedknuckle 270 of the shute strand 250 is similarly offset from the levelsof the depressed knuckles 220 of the Warp strand 200, although this isan incidental fact having no advantage in fiber formation.

Another difference concerns the mesh. The mesh of the wire shown inFIGS. 5 and 6 is x as compared with a mesh of 75 x 58 in the wire shownin FIGS. 3 and 4. These are representative meshes within a range ofmeshes suitable for various grades of paper. It will be noted that theopenings in the mesh are elongated longitudinally in the direction ofthe warp in the construction shown in FIGS. 3 and 4 and are elongatedlaterally in the direction of the shute or weft strands in theembodiment shown in FIGS. 5 and 6. The increase in the number of shutestrands not only compensates for some reduction in bearing and supportsurfaces due to the offset knuckles of the warp but it also is animportant factor in random orientation of the fiber. In practice thishas been found to contribute materially to the cross-machine strength ofthe paper, reducing the ratio of machine direct strength tocross-machine strength to a value below 2 to 1. Experimentally ratios of1 to 1 have been approximated.

In general, when the Wire is to be used in the production of tissue, asmaller and softer shute wire is used. It is very important for thepurposes of the present invention that all warp and shute wiresrespectively be uniform in their respective physicalcharacteristics-tensile strength, elongation yield, size, and surfacefinish. It is also very important that the weaving conditions beuniformly repetitive.

As in most Wire weaving, it is desirable in the making of eitherembodiment as herein disclosed that the tension on the heddles bedesirably adjusted for A inch line wire or thereabouts. In other words,the shed is centered from to A2 inch below a plane which is tangent tothe supply guide roll and the breast roll. It is also true of bothembodiments that the shute wire is preferably (not necessarily) ofsmaller cross section than the warp and that the impact in heat up isordinarily lighter than required for a semi-twill.

Preferably, though not necessarily, the shed of the loom is reversedbefore beat up, thus locking the weft between the warp wires immediatelybefore beat up occurs. This makes it easier to achieve the uniformsymmetry of the high knuckles of the weft without appreciable lateraldistortion of the Warp, thus preserving the uniform distribution of thedrain openings through the wire.

Despite the finer mesh, and the greater extent and broader bearing ofthe knuckles of full twill, the full twill gives drainage which iscomparable to a much larger mesh of semi-twill. Hence, despite thebetter fiber retention and orientation, drainage proceeds rapidly. Theexpensive fillers are, of course, retained along with the fiber, thusreducing loss of filler as well as loss of fiber.

I claim:

1. A paper making wire comprising an endless screen of full twill weaveand comprising warp strands of at least approximately seventy mesh andshute strands in pressure interlock therewith at points of crossing,said pressure interlock functioning to stabilize the wire againstdiagonal distortion, the warp strands and shute strands having knucklesin a symmetrical organization in which individual knuckles are curvedsymmetrically and the warp strand knuckles have substantially identicaloffset upwardly and downwardly and the shute strand knuckles have atleast substantially as much offset as the warp strand knuckles.

2. A paper making wire comprising an endless screen of full twill weaveand comprising warp strands of at least approximately seventy mesh andshute strands in pressure interlock therewith at points of crossing,said pressure interlock functioning to stabilize the wire againstdiagonal distortion, the warp strands and shute strands having knucklesin a symmetrical organization in which individual knuckles are curvedsymmetrically and the warp strand knuckles have substantially identicaloffset upwardly and downwardly and the shute strand knuckles have atleast substantially as much olfset as the warp strand knuckles, the warpstrands and shute strands defining a mesh having generally rectangularopenings substantially uniform in size of a form elongated transverselyof the wire in the direction of the shute strands.

3. A paper making wire comprising an endless screen of full twill weaveand comprising warp strands of at least approximately seventy mesh andshute strands in pressure interlock therewith at points of crossing,said pressure interlock functioning to stabilize the wire againstdiagonal distortion, the warp strands and shute strands having knucklesin a symmetrical organization in which individual knuckles are curvedsymmetrically and the Warp strand knuckles have substantially identicaloffset upwardly and downwardly and the shute strand knuckles have atleast substantially as much offset as the warp strand knuckles, the warpstrands and shute strands de fining a mesh having generally rectangularopenings substantially uniform in size of a form elongatedlongitudinally of the wire in the direction of the work strands.

4. A paper making wire comprising an endless screen of full twill weaveand comprising warp strands of at least approximately seventy mesh andshute strands in pressure interlock therewith at points of crossing,said pressure interlock functioning to stabilize the wire againstdiagonal distortion, the warp strands and shute strands having knucklesin a symmetrical organization in which individual knuckles are curvedsymmetrically and the warp strand knuckles have substantially identicaloffset upwardly and downwardly and the shute strand knuckles projectingupwardly on the paper making face of the wire to a level which is higherthan the level of the warp strand knuckles.

References Cited by the Examiner UNITED STATES PATENTS 1,103,943 7/14Coups 139-4255 1,678,941 7/28 Helman 139-425 1,920,495 8/33 Brown139-425 1,927,498 9/33 Lindsay et al 139-4255 2,007,862 7/ 35 Hurxthal245-10 2,199,417 5/40 Purves 139425.5 2,227,669 1/41 Parrett 139-4255 X2,462,604 2/49 Boucher 139-4255 X 2,728,358 12/55 Kools 139-4252,992,681 7/ 61 Hornbostel et al.

OTHER REFERENCES Monel Wire Screen and Filter Cloth, Bulletin H-3, pp.5, 6 and 7, by the International Nickel Company, 1110., 1940.

Pulp and Paper Manufacture, vol. 3, 1953, pages 92, and 121.

DONALD W. PARKER, Primary Examiner.

RICHARD D. NEVIUS, RUSSELL C. MADER,

Examiners.

1. A PAPER MAKING WIRE COMPRISING AN ENDLESS SCREEN OF FULL TWILL WEAVEAND COMPRISING WARP STRANDS OF AT LEAST APPROXIMATELY SEVENTY MESH ANDSHUTE STRANDS IN PRESSURE INTERLOCK THEREWITH AT POINTS OF CROSSING,SAID PRESSURE INTERLOCK FUNCTIONING TO STABLIZE THE WIRE AGAINSTDIAGONAL DISTORTION, THE WARP STRANDS AND SHUTE STRANDS HAVING KNUCKLESIN SYMMETRICAL ORGANIZATION IN WHICH INDIVIDUAL KNUCKLES ARE CURVEDSYMMETRICALLY AND THE WARP STRAND KNUCKLES HAVE SUBSTANTIALLY INDENTICALOFFSET UPWARDLY AND DOWNWARDLY AND THE SHUTE STRAND KNUCKLES HAVE ATLEAST SUBSTANTIALLY AS MUCH OFFSET AS THE WARP STRAND KNUCKLES.